全文获取类型
收费全文 | 1911篇 |
免费 | 114篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 31篇 |
综合类 | 2篇 |
化学工业 | 513篇 |
金属工艺 | 20篇 |
机械仪表 | 51篇 |
建筑科学 | 75篇 |
矿业工程 | 1篇 |
能源动力 | 69篇 |
轻工业 | 224篇 |
水利工程 | 19篇 |
石油天然气 | 4篇 |
无线电 | 186篇 |
一般工业技术 | 300篇 |
冶金工业 | 202篇 |
原子能技术 | 4篇 |
自动化技术 | 327篇 |
出版年
2024年 | 4篇 |
2023年 | 22篇 |
2022年 | 89篇 |
2021年 | 109篇 |
2020年 | 54篇 |
2019年 | 61篇 |
2018年 | 74篇 |
2017年 | 56篇 |
2016年 | 85篇 |
2015年 | 65篇 |
2014年 | 85篇 |
2013年 | 128篇 |
2012年 | 109篇 |
2011年 | 124篇 |
2010年 | 119篇 |
2009年 | 119篇 |
2008年 | 109篇 |
2007年 | 77篇 |
2006年 | 65篇 |
2005年 | 66篇 |
2004年 | 39篇 |
2003年 | 57篇 |
2002年 | 51篇 |
2001年 | 30篇 |
2000年 | 16篇 |
1999年 | 28篇 |
1998年 | 27篇 |
1997年 | 19篇 |
1996年 | 13篇 |
1995年 | 19篇 |
1994年 | 17篇 |
1993年 | 8篇 |
1992年 | 8篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 8篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1978年 | 3篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1964年 | 2篇 |
1946年 | 1篇 |
排序方式: 共有2028条查询结果,搜索用时 0 毫秒
91.
Michele A. Lewis Joseph G. Masin Patrick A. O'Hare 《International Journal of Hydrogen Energy》2009,34(9):4115-4124
The Nuclear Hydrogen Initiative (NHI) of the U.S. Department of Energy′s Office of Nuclear Energy Science and Technology is supporting an effort to reevaluate thermochemical cycles reported in the literature as having both promising efficiencies and proof-of-concept results. Recognizing that the calculation of efficiencies was not always consistently done or well defined in the literature, we first developed a consistent methodology for reevaluating the candidate thermochemical cycles. This methodology was defined for three levels of maturity in process knowledge. Argonne National Laboratory and a group of universities recalculated the efficiency for each level and identified the most critical R&D necessary to further assess the cycles' potential. This methodology is illustrated with the Cu–Cl in Part I of this series of three papers. Current results of the analyses for all of the cycles are summarized in Part II. Part III contains a more detailed Level 3 analysis for the Cu–Cl cycle. 相似文献
92.
93.
Multi-objective optimisation problems have seen a large impulse in the last decades. Many new techniques for solving distinct variants of multi-objective problems have been proposed. Production scheduling, as with other operations management fields, is no different. The flowshop problem is among the most widely studied scheduling settings. Recently, the Iterated Greedy methodology for solving the single-objective version of the flowshop problem has produced state-of-the-art results. This paper proposes a new algorithm based on Iterated Greedy technique for solving the multi-objective permutation flowshop problem. This algorithm is characterised by an effective initialisation of the population, management of the Pareto front, and a specially tailored local search, among other things. The proposed multi-objective Iterated Greedy method is shown to outperform other recent approaches in comprehensive computational and statistical tests that comprise a large number of instances with objectives involving makespan, tardiness and flowtime. Lastly, we use a novel graphical tool to compare the performances of stochastic Pareto fronts based on Empirical Attainment Functions. 相似文献
94.
The aim of this paper is to present a picture of student experience of a collaborative e-learning module in an asynchronous e-learning environment. A distance learning module on music education worth five credit points for a bachelor online degree for primary school educating teachers was assessed using a self-evaluation questionnaire that gathered quantitative and qualitative data about student satisfaction of the collaborative e-learning activity. The quantitative part of the questionnaire consisted of 27 closed questions on a 10-point Likert scale and offered data about satisfaction with the module. The qualitative part of the questionnaire provided an insight into the participant perspective of the online collaborative experience. General open questions on satisfaction and dissatisfaction were analyzed with an inductive analysis which showed the evaluation criteria used by 92 students. Results of the analysis showed five themes of the participants’ perspectives, which were interpreted by the researcher as: teamwork, cognitive, operating, organizing, and emotive/ethic for the positive aspects and teamwork, operating, organizing, and emotive/ethic for the aspects to be improved. The aspects that were associated with satisfaction include: collaborating, comparing ideas, sharing knowledge and skills to support each other, peer learning, analyzing and integrating different points of view, the usability of the platform, group planning and workload management. Aspects of the student learning experience that should inform the improvements of e-learning include: more collaboration between students since some students engage differently; more coordination and organization, the workload management in the group activities, some technical problems such as updating modifications. The participants’ results in the module increased their didactic potential as primary school teachers. The findings are discussed in relation to their potential impact on developing collaborative activities addressed to teacher education in distance learning. Implications for future research are also considered. 相似文献
95.
Gianluca Bianchi Fasani Francesca Bozzano Michele Cercato 《Bulletin of Engineering Geology and the Environment》2011,70(4):533-542
There are many abandoned underground mines beneath the city of Rome, created in the Pleistocene pyroclastic deposits over
thousands of years. These pose a serious public safety risk hence the study was undertaken to better assess the stability
of the underground workings. The Villa de Sanctis public park was selected as a suitable test site, as in this area the cavity
network can be inspected and the different steps of the progressive migration of voids toward the surface can be identified.
In addition to an underground geological survey, geophysical investigations were undertaken to elucidate some key characteristics
of the involved lithological units, including elastic stiffness and layer thickness. Recommendations are made for further
studies of the accessible and inaccessible areas. 相似文献
96.
A modeling method aimed at eliminating the need of explicit crack representation in bi-dimensional structures is presented
for the simulation of the initiation and subsequent propagation within composite materials. This is achieved by combining
a meshless method with a physical stress–displacement based criterion known as Cohesive Model. This model consents to apply
a penalty-based approach to delamination modeling where a variable penalty factor along the crack segment allows to loosen
or tight the two parts according to their relative displacements. Results are showed for classical single mode loading benchmark
cases and compared to experimental results taken from the literature. 相似文献
97.
Sinico Michele; Parovel Giulia; Casco Clara; Anstis Stuart 《Canadian Metallurgical Quarterly》2009,35(4):948
We show that human observers strongly underestimate a linear or circular trajectory that a luminous spot follows in the dark. At slow speeds, observers are relatively accurate, but, as the speed increases, the size of the path is progressively underestimated, by up to 35%. The underestimation imposes little memory load and does not require tracking of the trajectory. Most importantly, we found that underestimation occurred only when successive motion vectors changed in direction. This suggests a perceptual rather than representational origin of the illusion, related to vector-sum integration over time of neural motion signals in different directions. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
98.
Karel Michele J.; Knight Bob G.; Duffy Michael; Hinrichsen Gregory A.; Zeiss Antonette M. 《Canadian Metallurgical Quarterly》2010,4(2):75
Professional geropsychology is a growing area of practice and training. To meet the mental health needs of an aging population, increasing numbers of psychologists need to develop competence to work with older adults, their families, and related care systems. The Pikes Peak model for geropsychology training (Knight, Karel, Hinrichsen, Qualls, & Duffy, 2009) delineates attitude, knowledge, and skill competencies for professional geropsychology practice and makes recommendations for training. In this paper, we define and illustrate the Pikes Peak geropsychology practice competencies through a case example. In the case, an older man with complex needs seeks care through a generalist psychologist in an outpatient setting. The attitudes, knowledge, and skills that the psychologist needs to consider, and implications for training, are reviewed. Training recommendations and resources are provided, with a focus on the training needs of psychologists who wish to expand their practices to include older adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
99.
Vujasinovic Marko Ivezic Nenad Kulvatunyou Boonserm Barkmeyer Edward Missikoff Michele Taglino Francesco Marjanovic Zoran Miletic Igor 《Internet Computing, IEEE》2010,14(1):52-63
The authors discuss a semantic-mediation architecture to advance traditional approaches for standards-based business-to-business (B2B) interoperability. The architecture is supported by the Athena Knowledge Representation and Semantics Mediation tool suite. Initial experimentations with the architecture and the toolset offer discussions of key architectural and functional aspects and suggest directions for future tools enhancements. 相似文献
100.
Michele Leonardi Urszula Skomra Monika Agacka Anna Stochmal Katarzyna E. Ambryszewska Wieslaw Oleszek Guido Flamini Luisa Pistelli 《International Journal of Food Science & Technology》2013,48(8):1770-1774
Polish cultivars of hop (Humulus lupulus L.) are well known as aroma and bitter raw material in the brewing industry. To characterise four popular Polish hop cultivars, Lubelski (Lublin), Marynka, Sybilla and Iunga (also known as Junga), the essential oil profiles were determined by gas chromatography/flame ionisation detector (GC‐FID) and gas chromatography/chemical ionisation mass spectrometry (GC‐CIMS) and the alpha/beta acids amounts by high‐performance liquid chromatography/diode array detector (HPLC‐DAD) analysis. In addition, the multivariate statistical analysis of the volatile profiles was performed. The results obtained evidenced qualitative and quantitative differences between the four cultivars studied and the foreign hops described in the literature. Lubelski and Iunga showed the typical chemical profile of the fine‐aroma and high‐alpha cultivars, respectively. In Marynka and Sybilla, the average amounts of alpha acids were similar to the bitter hops, but with a volatile profile characteristics of the fine‐aroma and aroma cultivars respectively. 相似文献